1. Field of the Invention
The present invention relates to a balloon type ultrasonic diagnostic probe used for medical purposes.
2. Description of the Related Art
For the medical diagnosis of a patient, an ultrasonic diagnostic probe, having an ultrasonic sensor therein, has been developed. The ultrasonic diagnostic probe is used on the surface of the body, and also in body cavities, to carry out ultrasonic scanning. Ultrasonic scanning in the body cavity provides doctors with more precise data. In the ultrasonic scanning in the body cavity, however, the patient may feel pain during the insertion of the ultrasonic diagnosis probe into the esophagus, and it is required that ultrasonic diagnostic probes have smaller diameters.
Examples of prior art ultrasonic diagnostic probes as shown in FIGS. 7 to 10 of the attached drawings, are used to produce trans-esophageal echo cardiographs. In FIG. 7, the ultrasonic diagnosis probe 1 comprises an array 3 of elongated piezoelectric elements at the free end of the probe 1. Each of the piezoelectric elements is an elongated strip and the array 3 has a rectangular shape with long sides and short sides. The array of piezoelectric elements is arranged in the free end of the probe 1 so that the ultrasonic scanning direction is perpendicular to the longitudinal axis of the ultrasonic diagnostic probe 1. The length of the array 3 in the scanning direction is made small to mitigate the pain inflicted on the patient during the insertion of the ultrasonic diagnosis probe 1 into the body.
In this design, however, an aperture of the sensor becomes smaller if the length of the array 3 elements in the scanning direction is made smaller, and this reduces the quality of obtained images. In addition, since the scanning direction is fixedly determined, only a restricted picture can be obtained.
In FIG. 8, the probe 1 has an array of piezoelectric elements 3 the scanning direction of which coincides with the longitudinal direction of the probe 1. This probe can overcome the problem of the diameter of the sensor, but still suffers from the problem of its small degree of freedom in obtaining a picture.
To solve these problems, a bi-planar-type probe 1 having two arrays 3 of piezoelectric elements having the scanning directions perpendicular to each other is shown in FIG. 9. Also, a multi-planar-type probe 1 having a rotatable array 3 of piezoelectric elements has been proposed, as shown in FIG. 10. However, since the former includes the array 3 of the piezoelectric elements having the scanning direction parallel to the longitudinal direction of the probe 1, and since the latter needs space for the array 3 to piezoelectric elements rotate, these probes also suffer from the problem that the free end of the probe 1 must have a large size. Therefore, these designs inflict great pain on the patient.